Bicycle riding is an enjoyable mode of transportation, because riding a bicycle is environmentally benign and is also a pleasant and healthful exercise. Moreover, bicycling to work is less expensive than commuting by car. Not surprisingly, many people commute to and from work on bicycles.
As recognized herein, for daily bicycling to and from work, particularly at distances that exceed a few miles, it can be advantageous to provide a motorized assist to selectively aid a rider in propelling a bicycle. Likewise, a motorized assist to a bicycle rider can be helpful on long sojourns undertaken for exercise or vacation.
The present invention understands that bicycles which can be pedalled by a rider have been provided that can be propelled not only by pedal power, but alternatively by means of a motor that is mounted on the frame of the bicycle. An example of such an apparatus is the so-called "Moped", which can either be pedalled by a rider, or be propelled by a motor. Such devices, however, cannot be both pedalled and powered by a motor simultaneously. Indeed, so-called "Mopeds" essentially are motorcycles that can be pedalled only at low speeds, while the motor is disengaged from the drive assembly. When the motor is engaged with the drive assembly, the apparatus cannot be pedalled. Thus, the motors of so-called "Mopeds" replace pedalling altogether, and consequently "Mopeds" defeat the purpose of the present invention in providing a means to assist a rider in pedalling a bicycle over long distances.
Additionally, U.S. Pat. Nos. 5,361,863 and 5,242,028 disclose motorized bicycles that incorporate motors in propelling bicycles. Unfortunately, the devices disclosed in the '863 and '028 patents suffer from several drawbacks. These drawbacks include motors being mounted on the bicycle forward of the seat, thereby potentially impeding the leg action of a rider and undesirably shifting the centers of gravity of the bicycles forward from where the centers of gravity otherwise would be. Moreover, the clutch disclosed in the '028 patent would appear to be less robust than is required for prolonged use, and the '863 patent does not disclose in any detail the clutch that it is intended to incorporate.
Further, with particular regard to the '028 patent, the use of an electric motor is required, which in turn requires that a relatively heavy, cumbersome twelve volt battery be mounted on the bicycle. On the other hand, to couple the '863 motor with the drive shaft while achieving the necessary speed reduction, the '863 patent incorporates plural spur gears which consume space in the transverse dimension, thereby further potentially impeding the leg action of the rider. Additionally, the '863 patent teaches that its power transmission assembly requires that the motor be mounted with the crankshaft oriented transversely on the bicycle, which in turn requires that the conventional crankshaft be modified as taught by the '863 patent. As recognized by the present invention, it is preferable to avoid modifying the crankshaft of a conventional motor, because such modifications can be costly and time-consuming procedures.
As further recognized by the present invention, it is possible to provide a motorized bicycle that uses a lightweight gasoline motor without requiring modifications to the motor, and without impeding the leg action of a rider. Accordingly, it is an object of the present invention to provide a motorized bicycle that can be pedalled by a rider simultaneously with being powered by a motor that does not impede the rider's leg action. Another object of the present invention is to provide a motorized bicycle that uses a strong, reliable gear system that can directly interface with the existing derailleur system of a bicycle. Still another object of the present invention is to provide a motorized bicycle that incorporates strong, reliable clutches to permit the bicycle to be pedalled by a rider simultaneously with being powered by a motor. Yet another object of the present invention is to provide a motorized bicycle that is easy to use and cost-effective to manufacture.